1. Field of the Invention
The present invention relates to an image pickup apparatus using a microlens array.
2. Description of the Related Art
Various image pickup apparatuses have been proposed and developed. Image pickup apparatuses performing predetermined image processing on image pickup data obtained by imaging or picking up an image to output the image pickup data have been proposed.
For example, International Patent Publication No. 06/039486 and Ren.Ng, et al. “Light Field Photography with a Hand-Held Plenoptic Camera”, Stanford Tech Report CTSR 2005-02, propose image pickup apparatuses using a technique called “Light Field Photography”. Such an image pickup apparatus includes an image pickup lens, a microlens array, an image pickup device and an image processing section, and an aperture stop including a single aperture in its central part is included in the image pickup lens. In such a configuration, image pickup data obtained by the image pickup device includes the intensity distribution of light on a light-sensing plane as well as information on the traveling direction of the light. Thereby, the image processing section is capable of reconstructing or reproducing an image viewed from an arbitrary viewpoint or an arbitrary direction (hereinafter simply referred to as a field of view).
An image obtained by a photographic apparatus (a light field camera) embodying the technique by “Light Field Photography” is outputted as an image group in which a plurality of circular images are arranged in an array as illustrated in, for example, FIG. 11 of International Patent Publication No. 06/039486. Such a circular image corresponds to an image (hereinafter referred to a unit image), which is formed on a solid-state image pickup device by each microlens according to an exit pupil shape of a photographing lens.
Moreover, light-sensing sections of a solid-state image pickup apparatus are generally arranged for each of pixels in rows and columns at a predetermined pitch. Since a circuit section such as a transfer region is arranged around the light-sensing section of each of the pixels, so light entering such a region does not contribute to image pickup. Therefore, in most of solid-state image pickup devices, a light-condensing section (such as a light-refracting configuration) condensing light entering a region other than the light-sensing section is arranged to guide the light to the light-sensing section, thereby higher sensitivity is achieved.
In this case, when a light-refracting configuration such as an on-chip lens is arranged directly on each pixel around the optical axis center of an optical system, most of light rays are able to be condensed effectively. However, a main light ray is inclined in a peripheral area away from the optical axis. Therefore, for example, as described in Japanese Patent Nos. 2600250 and 3170847, image height correction is performed so that a pitch between on-chip lenses becomes smaller than a pixel pitch, and that a gap between a center position of the on-chip lens and a pixel center position of each pixel is gradually increased with distance from the optical axis.